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linux/Documentation/core-api/timekeeping.rst

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Documentation: document ktime_get_*() APIs As Dave Chinner points out, we don't have a proper documentation for the ktime_get() family of interfaces, making it rather unclear which of the over 30 (!) interfaces one should actually use in a driver or elsewhere in the kernel. I wrote up an explanation from how I personally see the interfaces, documenting what each of the functions do and hopefully making it a bit clearer which should be used where. This is the first time I tried writing .rst format documentation, so in addition to any mistakes in the content, I probably also introduce nonstandard formatting ;-) I first tried to add an extra section to Documentation/timers/timekeeping.txt, but this is currently not included in the generated API, and it seems useful to have the API docs as part of what gets generated in https://www.kernel.org/doc/html/latest/core-api/index.html#core-utilities instead, so I started a new file there. I also considered adding the documentation inline in the include/linux/timekeeping.h header, but couldn't figure out how to do that in a way that would result both in helpful inline comments as well as readable html output, so I settled for the latter, with a small note pointing to it from the header. Cc: Dave Chinner <david@fromorbit.com> Cc: John Stultz <john.stultz@linaro.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Stephen Boyd <sboyd@kernel.org> Tested-by: Randy Dunlap <rdunlap@infradead.org> Reviewed-by: Randy Dunlap <rdunlap@infradead.org> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2018-07-10 16:46:41 +02:00
timekeeping: Use proper clock specifier names in functions This makes boot uniformly boottime and tai uniformly clocktai, to address the remaining oversights. Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Arnd Bergmann <arnd@arndb.de> Link: https://lkml.kernel.org/r/20190621203249.3909-2-Jason@zx2c4.com
2019-06-21 22:32:48 +02:00
Documentation: document ktime_get_*() APIs As Dave Chinner points out, we don't have a proper documentation for the ktime_get() family of interfaces, making it rather unclear which of the over 30 (!) interfaces one should actually use in a driver or elsewhere in the kernel. I wrote up an explanation from how I personally see the interfaces, documenting what each of the functions do and hopefully making it a bit clearer which should be used where. This is the first time I tried writing .rst format documentation, so in addition to any mistakes in the content, I probably also introduce nonstandard formatting ;-) I first tried to add an extra section to Documentation/timers/timekeeping.txt, but this is currently not included in the generated API, and it seems useful to have the API docs as part of what gets generated in https://www.kernel.org/doc/html/latest/core-api/index.html#core-utilities instead, so I started a new file there. I also considered adding the documentation inline in the include/linux/timekeeping.h header, but couldn't figure out how to do that in a way that would result both in helpful inline comments as well as readable html output, so I settled for the latter, with a small note pointing to it from the header. Cc: Dave Chinner <david@fromorbit.com> Cc: John Stultz <john.stultz@linaro.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Stephen Boyd <sboyd@kernel.org> Tested-by: Randy Dunlap <rdunlap@infradead.org> Reviewed-by: Randy Dunlap <rdunlap@infradead.org> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2018-07-10 16:46:41 +02:00
timekeeping: Add missing _ns functions for coarse accessors This further unifies the accessors for the fast and coarse functions, so that the same types of functions are available for each. There was also a bit of confusion with the documentation, which prior advertised a function that has never existed. Finally, the vanilla ktime_get_coarse() was omitted from the API originally, so this fills this oversight. Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Arnd Bergmann <arnd@arndb.de> Link: https://lkml.kernel.org/r/20190621203249.3909-3-Jason@zx2c4.com
2019-06-21 22:32:49 +02:00
Documentation: document ktime_get_*() APIs As Dave Chinner points out, we don't have a proper documentation for the ktime_get() family of interfaces, making it rather unclear which of the over 30 (!) interfaces one should actually use in a driver or elsewhere in the kernel. I wrote up an explanation from how I personally see the interfaces, documenting what each of the functions do and hopefully making it a bit clearer which should be used where. This is the first time I tried writing .rst format documentation, so in addition to any mistakes in the content, I probably also introduce nonstandard formatting ;-) I first tried to add an extra section to Documentation/timers/timekeeping.txt, but this is currently not included in the generated API, and it seems useful to have the API docs as part of what gets generated in https://www.kernel.org/doc/html/latest/core-api/index.html#core-utilities instead, so I started a new file there. I also considered adding the documentation inline in the include/linux/timekeeping.h header, but couldn't figure out how to do that in a way that would result both in helpful inline comments as well as readable html output, so I settled for the latter, with a small note pointing to it from the header. Cc: Dave Chinner <david@fromorbit.com> Cc: John Stultz <john.stultz@linaro.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Stephen Boyd <sboyd@kernel.org> Tested-by: Randy Dunlap <rdunlap@infradead.org> Reviewed-by: Randy Dunlap <rdunlap@infradead.org> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2018-07-10 16:46:41 +02:00
timekeeping: Add missing _ns functions for coarse accessors This further unifies the accessors for the fast and coarse functions, so that the same types of functions are available for each. There was also a bit of confusion with the documentation, which prior advertised a function that has never existed. Finally, the vanilla ktime_get_coarse() was omitted from the API originally, so this fills this oversight. Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Arnd Bergmann <arnd@arndb.de> Link: https://lkml.kernel.org/r/20190621203249.3909-3-Jason@zx2c4.com
2019-06-21 22:32:49 +02:00
timekeeping: Boot should be boottime for coarse ns accessor Somewhere in all the patchsets before, this cleanup got lost. Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Arnd Bergmann <arnd@arndb.de> Link: https://lkml.kernel.org/r/20190624091539.13512-1-Jason@zx2c4.com
2019-06-24 11:15:39 +02:00
timekeeping: Add missing _ns functions for coarse accessors This further unifies the accessors for the fast and coarse functions, so that the same types of functions are available for each. There was also a bit of confusion with the documentation, which prior advertised a function that has never existed. Finally, the vanilla ktime_get_coarse() was omitted from the API originally, so this fills this oversight. Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Arnd Bergmann <arnd@arndb.de> Link: https://lkml.kernel.org/r/20190621203249.3909-3-Jason@zx2c4.com
2019-06-21 22:32:49 +02:00
Documentation: document ktime_get_*() APIs As Dave Chinner points out, we don't have a proper documentation for the ktime_get() family of interfaces, making it rather unclear which of the over 30 (!) interfaces one should actually use in a driver or elsewhere in the kernel. I wrote up an explanation from how I personally see the interfaces, documenting what each of the functions do and hopefully making it a bit clearer which should be used where. This is the first time I tried writing .rst format documentation, so in addition to any mistakes in the content, I probably also introduce nonstandard formatting ;-) I first tried to add an extra section to Documentation/timers/timekeeping.txt, but this is currently not included in the generated API, and it seems useful to have the API docs as part of what gets generated in https://www.kernel.org/doc/html/latest/core-api/index.html#core-utilities instead, so I started a new file there. I also considered adding the documentation inline in the include/linux/timekeeping.h header, but couldn't figure out how to do that in a way that would result both in helpful inline comments as well as readable html output, so I settled for the latter, with a small note pointing to it from the header. Cc: Dave Chinner <david@fromorbit.com> Cc: John Stultz <john.stultz@linaro.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Stephen Boyd <sboyd@kernel.org> Tested-by: Randy Dunlap <rdunlap@infradead.org> Reviewed-by: Randy Dunlap <rdunlap@infradead.org> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2018-07-10 16:46:41 +02:00
Documentation: fix typo CLOCK_MONONOTNIC_COARSE Fix typo in documentation file timekeeping.rst: CLOCK_MONONOTNIC_COARSE should be CLOCK_MONOTONIC_COARSE. Signed-off-by: Aurelien Thierry <aurelien.thierry@quoscient.io> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2019-06-07 10:07:02 +02:00
Documentation: document ktime_get_*() APIs As Dave Chinner points out, we don't have a proper documentation for the ktime_get() family of interfaces, making it rather unclear which of the over 30 (!) interfaces one should actually use in a driver or elsewhere in the kernel. I wrote up an explanation from how I personally see the interfaces, documenting what each of the functions do and hopefully making it a bit clearer which should be used where. This is the first time I tried writing .rst format documentation, so in addition to any mistakes in the content, I probably also introduce nonstandard formatting ;-) I first tried to add an extra section to Documentation/timers/timekeeping.txt, but this is currently not included in the generated API, and it seems useful to have the API docs as part of what gets generated in https://www.kernel.org/doc/html/latest/core-api/index.html#core-utilities instead, so I started a new file there. I also considered adding the documentation inline in the include/linux/timekeeping.h header, but couldn't figure out how to do that in a way that would result both in helpful inline comments as well as readable html output, so I settled for the latter, with a small note pointing to it from the header. Cc: Dave Chinner <david@fromorbit.com> Cc: John Stultz <john.stultz@linaro.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Stephen Boyd <sboyd@kernel.org> Tested-by: Randy Dunlap <rdunlap@infradead.org> Reviewed-by: Randy Dunlap <rdunlap@infradead.org> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2018-07-10 16:46:41 +02:00
timekeeping: Introduce fast accessor to clock tai Introduce fast/NMI safe accessor to clock tai for tracing. The Linux kernel tracing infrastructure has support for using different clocks to generate timestamps for trace events. Especially in TSN networks it's useful to have TAI as trace clock, because the application scheduling is done in accordance to the network time, which is based on TAI. With a tai trace_clock in place, it becomes very convenient to correlate network activity with Linux kernel application traces. Use the same implementation as ktime_get_boot_fast_ns() does by reading the monotonic time and adding the TAI offset. The same limitations as for the fast boot implementation apply. The TAI offset may change at run time e.g., by setting the time or using adjtimex() with an offset. However, these kind of offset changes are rare events. Nevertheless, the user has to be aware and deal with it in post processing. An alternative approach would be to use the same implementation as ktime_get_real_fast_ns() does. However, this requires to add an additional u64 member to the tk_read_base struct. This struct together with a seqcount is designed to fit into a single cache line on 64 bit architectures. Adding a new member would violate this constraint. Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Link: https://lore.kernel.org/r/20220414091805.89667-2-kurt@linutronix.de
2022-04-14 11:18:03 +02:00
Documentation: document ktime_get_*() APIs As Dave Chinner points out, we don't have a proper documentation for the ktime_get() family of interfaces, making it rather unclear which of the over 30 (!) interfaces one should actually use in a driver or elsewhere in the kernel. I wrote up an explanation from how I personally see the interfaces, documenting what each of the functions do and hopefully making it a bit clearer which should be used where. This is the first time I tried writing .rst format documentation, so in addition to any mistakes in the content, I probably also introduce nonstandard formatting ;-) I first tried to add an extra section to Documentation/timers/timekeeping.txt, but this is currently not included in the generated API, and it seems useful to have the API docs as part of what gets generated in https://www.kernel.org/doc/html/latest/core-api/index.html#core-utilities instead, so I started a new file there. I also considered adding the documentation inline in the include/linux/timekeeping.h header, but couldn't figure out how to do that in a way that would result both in helpful inline comments as well as readable html output, so I settled for the latter, with a small note pointing to it from the header. Cc: Dave Chinner <david@fromorbit.com> Cc: John Stultz <john.stultz@linaro.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Stephen Boyd <sboyd@kernel.org> Tested-by: Randy Dunlap <rdunlap@infradead.org> Reviewed-by: Randy Dunlap <rdunlap@infradead.org> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2018-07-10 16:46:41 +02:00
docs: timekeeping: Use correct prototype for deprecated functions Use the correct prototypes for do_gettimeofday(), getnstimeofday() and getnstimeofday64(). All of these returned void and passed the return value by reference. This should make the documentation of their deprecation and replacements easier to search for. Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz> Acked-by: Arnd Bergmann <arnd@arndb.de> Link: https://lore.kernel.org/r/20200414221222.23996-1-chris.packham@alliedtelesis.co.nz Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2020-04-15 10:12:22 +12:00
Documentation: document ktime_get_*() APIs As Dave Chinner points out, we don't have a proper documentation for the ktime_get() family of interfaces, making it rather unclear which of the over 30 (!) interfaces one should actually use in a driver or elsewhere in the kernel. I wrote up an explanation from how I personally see the interfaces, documenting what each of the functions do and hopefully making it a bit clearer which should be used where. This is the first time I tried writing .rst format documentation, so in addition to any mistakes in the content, I probably also introduce nonstandard formatting ;-) I first tried to add an extra section to Documentation/timers/timekeeping.txt, but this is currently not included in the generated API, and it seems useful to have the API docs as part of what gets generated in https://www.kernel.org/doc/html/latest/core-api/index.html#core-utilities instead, so I started a new file there. I also considered adding the documentation inline in the include/linux/timekeeping.h header, but couldn't figure out how to do that in a way that would result both in helpful inline comments as well as readable html output, so I settled for the latter, with a small note pointing to it from the header. Cc: Dave Chinner <david@fromorbit.com> Cc: John Stultz <john.stultz@linaro.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Stephen Boyd <sboyd@kernel.org> Tested-by: Randy Dunlap <rdunlap@infradead.org> Reviewed-by: Randy Dunlap <rdunlap@infradead.org> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2018-07-10 16:46:41 +02:00